The build-up of amyloid proteins in living tissue, a condition known as amyloidosis, is either the cause or a major factor in the pathology of many so-called amyloid diseases, for example Alzheimer's, Parkinson's, Huntington's, and prion diseases. Historically, aggregations of protein were classified as amyloid if they displayed apple-green birefringence under polarized light when stained with the dyes Congo red or Thioflavin T (ThT) (Sipe and Cohen, 2000, J. Struct. Biol. 130:88-98). That definition of amyloid has been expanded in modern times to apply to any polypeptide which can polymerize in a cross-β sheet conformation in vitro or in vivo, regardless of sequence (Xu, 2007, Amyloid 14:119-31). Certain types of amyloidosis may occur principally in the central nervous system, as with aggregation of beta-amyloid protein in Alzheimer's Disease, alpha-synuclein in Parkinson's Disease, huntingtin protein in Huntington's Disease, and prion protein in Creutzfeldt-Jacob and other prion diseases. Other types of amyloidosis are systemic in nature, as with aggregation of transthyretin in senile systemic amyloidosis.
One generic treatment currently being considered is immunological, based on antibodies that can bind a diverse collection of small amyloid oligomers (Kayed et al, 2003, Science 300:486-489); such work also demonstrates that there is a structural commonality among the oligomers of amyloid proteins, regardless of sequence. However, immunological therapies bring a high risk of potentially fatal adverse reactions due to cascade responses in the subject's own immune system, as a recent failed clinical trial has shown (Gilman et al, 2005, Neurology 64:1553-1562).
A more promising generic treatment, relevant to the present invention, utilizes the traditional approach of small molecules as modulators of disease targets, being amyloids in this case. A wide variety of compounds have shown the ability to inhibit the aggregation of amyloids in vitro, and many such compounds can inhibit the aggregation of beta-amyloid protein as well as other kinds of amyloid (see for example Klabunde et al, 2000, Nat. Struct. Biol. 7:312-321; Green et al, 2003, J. Am. Chem. Soc. 125:13404-13414; Masuda et al, 2006, Biochemistry 45:6085-6094; Ono et al, 2003, J. Neurochem 87:172-181; Tagliavini et al, 2000, J. Mol. Biol. 300:1309-1322). Some compounds have also been shown to have beneficial in vivo effects, including reducing the size of amyloid plaques and delaying mortality in mouse models of amyloid disease (Chen et al, 2000, Nat. Med. 6:797-801; Imbimbo et al, 2007, Pharmacol. Res. 55:318-328). Of special note is resveratrol, an antioxidant component of red wine and an inhibitor of beta-amyloid aggregation at an effective concentration of 5.6 μM (Riviere et al, 2007, Bioorg. Med. Chem., 15:1160-1167). Accordingly, it is reasonable to expect that compounds which inhibit the aggregation of beta-amyloid protein in vitro may have in vitro and in vivo effects that are beneficial for the treatment of amyloid diseases, particularly with respect to Alzheimer's Disease.
All of the above listed diseases are invariably fatal using current medical practice. In none of these diseases is there any known, widely accepted therapy or treatment that can halt and/or reverse the aggregation of amyloid deposits. As such there remains an urgent need for treatments such as those provided below.
The present invention pertains to methods and compositions useful for treating amyloidosis. The methods of the invention involve administering to a subject a therapeutic compound which inhibits amyloid aggregation. “Inhibition of amyloid aggregation” is intended to encompass prevention of amyloid deposition, inhibition of further amyloid deposition in a subject with ongoing amyloidosis, and reduction of amyloid deposits in a subject with ongoing amyloidosis. Inhibition of amyloid aggregation is determined relative to an untreated subject or relative to the treated subject prior to treatment. Amyloid aggregation is inhibited by interfering with the binding of monomeric and/or oligomeric amyloid protein to other, nearby amyloid protein such that aggregation of amyloid is inhibited. This inhibition of amyloid aggregation may have effects on both chain and step polymerization mechanisms of amyloid proteins, and may affect the aggregation of both heterogeneous and homogeneous amyloid deposits. Examples of amyloid proteins include, but are by no means limited to, beta-amyloid protein, tau protein, alpha-synuclein protein, immunoglobulin light chain protein, insulin, Islet amyloid polypeptide, lysozyme, transthyretin, amyloid A, prion protein, and polyglutamate (huntingtin) protein.
As stated above, resveratrol has been shown to inhibit the aggregation of beta-amyloid protein. The compounds of the present invention were identified using structure-based drug design and virtual screening techniques as having low energy conformations that overlap geometrically and electrostatically with resveratrol and which bind to a model of amyloid aggregation as disclosed in U.S. Provisional Application Ser. No. 61/092,826. More specifically, over 700,000 known, drug-like compounds were investigated computationally for this overlap, and several thousand compounds were identified.